Monday, April 22, 2013

The Best Corn Planting Dates Are Yet To Come

This year farmers have been challenged by cool, wet conditions during April. Snow is again forecast for later this week. Even though planting dates seem like they have been delayed, especially compared to 2012, we still have not passed the optimum planting dates for corn. Wisconsin farmers can plant a large number of acres quickly. Since 1979, there have been 5 years when 40% or more of the acres were planted in one week (1981, 1984, 1999, 2000, and 2004). Between May 2-9, 1999 and April 30-May 7, 2000 farmers planted 1.5 million acres in one week (42% and 44% of the acres planted in those years).

At the University of Wisconsin Agricultural Research Station in Arlington, we have established planting date trials since 1974. Multiple hybrids are established as soon as field conditions allow. In many years, snow is still in roadside ditches when the first planting date occurs. I pooled data for full-season hybrids with Relative Maturity ratings of 104 to 108 RM for the last 10 years (2003-2012).

The corn grain yield response to planting date is shown in Figure 1. The planting date producing maximum grain yield during this period is April 28. Yields were within 95% of the maximum yield from April 15 to May 12, a 28-day period. By May 10 grain yield is decreasing 0.9 bu/A per day and then accelerates to 2.6 bu/A per day on June 1. Grain yield risk (the spread of the data points around the regression line) is lowest in April and early May at + 14 bu/A and increases to + 45 bu/A in late May and early June.

Year affects the planting date when maximum yield occurs, the date of 95% maximum yield, and the yield loss acceleration during late May and early June (Table 1). The date when maximum yield occurs varies from April 10 to May 3. We were still within 95% of the maximum until April 29, 2005 and May 19, 2011.

Like last year the important thing to remember is patience. Be ready to go so that when field conditions are fit, you are ready to plant. Our standard planting date recommendation is to plant as quickly and safely as possible after April 20 in southern Wisconsin, and after April 30 in northern Wisconsin.